2003 RSV Rear Brake Spongy to No Pressure

[LibertarianCRF]

Riding last week and noted that the brake needed to be depressed further than normal to engage so I thought maybe and adjustment was needed before new pads.  Got clear into the "spongy" feel a few days later.  

Yesterday while riding it lost all resistance.  Spring was the only thing giving it any tension.  

Hooked up a vacuum pump and ran fresh fluid through it.  Never got a consistent stream of fluid into the collection tank and hose had lots of bubbles but I could watch the fluid going down on the resevoir.  It is back to spongy resistance and is braking the bike, but it's not 5 by 5 yet.  

I cannot see any clear leaks but I replaced the clutch spring and friction discs so I need to recheck it today now that I've gotten all of the oil cleaned up and given it an opportunity to leak again.  

 

[djh3]

I tried to vacuum bleed my RSV. Never got what I felt was a good stream. So I would bleed with the vacuum set up, then make a few pumps with the pedal nice and slow and it seemed to always worked good.

[Marcarl]

First you mention brakes, then you talk clutch, which is it?

[LibertarianCRF]

Mm.  That was unclear.  Rear brake is the issue.  I just replaced the clutch discs so I wasn't able to tell if the oil I'm seeing coating the lines is brake fluid from the brake lines, or oil from the case.  I'll take a look at it tonight.  

 

[RDawson]

Sometimes when you vacuum bleed air seeps around the threads of the bleeder. I always do the old pump n release a few times to finish up and make sure there’s no air left. . 

[M61A1MECH]

When I had my Goldwing, the brake bleeding process was very involved due it having linked brakes, I installed Speed Bleeders, those coupled with a catch pouch, I could do the whole process in a matter of minutes and never had an issue with air or spongey brakes.

http://www.speedbleeder.com/bikechart.htm 

[Marcarl]

2 hours ago, M61A1MECH said:

When I had my Goldwing, the brake bleeding process was very involved due it having linked brakes, I installed Speed Bleeders, those coupled with a catch pouch, I could do the whole process in a matter of minutes and never had an issue with air or spongey brakes.

http://www.speedbleeder.com/bikechart.htm 

I'm surprised that you had good luck with the GW, although linked it is a totally different system than the Venture.

 

[Marcarl]

I would check the master first. If there was a leak elsewhere, fluid would show up more likely.

[M61A1MECH]

7 hours ago, Marcarl said:

I'm surprised that you had good luck with the GW, although linked it is a totally different system than the Venture.

 

Agreed but the speed bleeders work on what ever system you install them, you can even use them on hydraulic clutches, they work very well and all with out the help of another person. 

[BlueSky]

My RSV rear brake quit working and the problem was the diaphragm in the master cylinder had fallen to the bottom and was blocking fluid flow!!!!!

[N3FOL]

On 5/29/2024 at 10:06 PM, BlueSky said:

My RSV rear brake quit working and the problem was the diaphragm in the master cylinder had fallen to the bottom and was blocking fluid flow!!!!!

From that statement, I am guessing the fluid went very low that caused your diaphragm to fall to the bottom.  With that said, it has been awhile since my last brake/clutch fluid replacement...but the fluid still looks good from the watch glass on both the clutch and front brakes.